The U.S. Fish and Wildlife Service is investigating the killing of a female Mexican gray wolf that had been denning with pups in New Mexico. The animal, known as F1108, was found in late June shot to death, authorities said. Her pups were assumed to be dead. The 6-year-old female was born in the wild, captured with her pack and placed in New Mexico's Sevilleta National Wildlife Refuge. She and a male were released in May and placed in a temporary pen in the Gila National Forest. The male, known as M1133, left the den site and appeared to be returning to Sevilleta, where he was born, when he was recaptured by wildlife authorities. The female whelped her pups, but signals from her radio collar indicated that she, too, was on the move. F1108 was found dead some distance from the Gila Wilderness. Federal authorities provided no further information except to say the case is under investigation. Endangered species protections for wolves in the Northern Rockies and Great Lakes were removed last month, but Mexican wolves were recognized as a sub-species and retain federal protections.